I wasn't in the room when it happened, but I was probably among the first dozen or so to hear the name -- and it was presented to me as both at once: "ZFS" was

I wasn't in the room when it happened, but I was probably among the first dozen or so to hear the name -- and it was presented to me as both at once: "ZFS" was both "the last word in filesystems" and (conveniently) a zettabyte. I remember Bonwick quickly pointing out that yes, a yottabyte was larger but "YFS" was passed over for obvious reasons.